GEaReD-Examples
In the following, we describe two major challenges and put them briefly in the context of GEaReD.
Challenge I: Temperature dependent yield loss in agriculture
For crops like wheat, it is already evident, that climate change and higher temperatures will severely negatively affect their yields in different areas on earth [1]. To increase or keep yields while temperature is rising, climate ready crops adapted to high temperatures and possible drought stress are needed. Drought tolerance in plants has been extensively studied and several approaches for improving the plants drought tolerance were identified. However, drought or stress responses are complex and exploitation of the identified traits in our crops is limited so far. GEaReD provide a new way to introduce complex traits for handling drought and other stresses in new breeding materials. Taking for example barley, instead of extensive breeding of cultivated barley cultivars which are adapted to optimal climate conditions, a re-domestication of wild barley Hordeum vulgare ssp .spontaneum from hot climates in The Middle East could be done. Introducing the major important domestication genes like btr ,thresh-1 or the photoperiod gene family ppd-H could be done with genome editing techniques (see Table I). Wild barley is already adapted to drought stress and may be armed to combat heat stress [12]. Re-Domestication could be a key way to quickly generate adapted cultivars for agriculture sustaining the coming climate conditions. In addition, a de novo domestication of exampleteosinte could be valuable. Teosinte originates from high temperate areas and is already adapted to high temperatures. Re-domestication via Genome Editing could potentially lead to new maize plants adapted to higher temperatures.
Challenge II: Extensive Soil use and fertilizer use in agriculture
Soil degradation threatens roughly 20% of global area and is a severe impact for food safety and security [13]. Different strategies are deployed to combat soil degradation, either by physical methods, chemical methods or biological methods. These methods range from No-Tilling cultivation, use of fertilizer or using organisms for bioremediation, respectively [13]. The depletion of nutrients from the soil and the extensive use of fertilizers and tilling/plowing or the use of cover crops has a further drawback. It increases the effort required by the farmer and results in an increased release of greenhouse gasses. A way to solve this would be to use perennial crops instead of annual crops. Perennial crops would support higher carbon binding in the soil, less fertilizer use, less use of farming equipment and soil erosion. Unfortunately, perennial grains developed by conventional breeding delivers lower grain yields decreasing for each consecutive year of growth [14, 15]. For many current annual crops, wild perennial relatives exist. Among the triticeae, barley has several close perennial relatives including H. bulbosum, H. chilense and H. brevisubulatum [16]. Wheat does not have as close perennial relatives however wide crosses with Thinopyrum spp. has been used in previous attempts to breed perennial wheat [17]. In addition, maize and rice has perennial relatives Zea diploperennis andOryza longistaminata respectively. Research with perennial rice, wheatgrass and other perennial plants clearly indicate the benefits over the use of annual alternatives. Even though the yield is usually not competitive, with exception for the perennial rice PR23 in its first year [15], the benefits for the soil, the farmer and the environment are clearly pointing toward the use of perennial crops. A GEaReD approach to the challenge of developing competitive perennial crops could be to strive for analogs of the current major crops by domestication their closest perennial relatives with the annual crop as a genetic roadmap.
Table I: Overview of some candidate domestication genes from different crops.